ATRP

Sandip Argekar

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ATRP

Atom Transfer Radical Polymerization

Halogen transfer through metal complex induced reversible heterolysis

resulting in the formation of reversible free radicals to

initiate and propagate polymerization.

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Formation of induced reversible free radical?

XRR – Propagating species/ tethered initiator X – halogen atom (usually Cl/Br)

Mn Mn – Transition metal in lower oxidation state (Copper is most commonly used)

. .Ligand – Lewis base to stabilize transition metal

forming a complex

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Formation of induced reversible free radical?

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ATRP types

• Normal ATRP• Reverse ATRP– Introduce higher oxidation state metal – Reaction results in lesser concentration of radicals– More control and better PDI

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• Simultaneous Normal & Reverse ATRP (SR&NI)– Add small amount of free radical initiator– Allows reaction propagation for active catalysts

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• Activator Generated Electron Transfer ATRP– Reducing agent induced activation– Allows catalysts to be added in their stable state

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Why ATRP?

Control

Compositions Topology Functionality

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Composition• Statistical polymer– Reactivity ratios

• Block copolymers– Macro initiators– ABC type copolymers

• Gradient copolymers

X

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Topology

Simplearchitecture

Complex architecture

Linear

Graft copolymers

Brush copolymers

Star polymers

Surface modification

Star shaped copolymers

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Functionality

• Functional monomers– eg. Glycidyl methacrylate

• Modification post polymerization• Functional ATRP initiators– eg. Glycidyl 2-bromopropionate

• End-group transformation chemistry

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Shortcomings of ATRP

• Oxygen hinders polymerization forming stable copper oxides. – Degassing– Addition of reducing agent (Cu) provides tolerance

• No control over tacticity due to radical nature.• Unwanted catalyst color• Catalyst removal problems

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References• Matyjaszewski Group – Research

http://www.chem.cmu.edu/groups/maty/about/research/index.html

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